The present invention relates generally to the field of suspension systems for vehicles. More particularly, the present invention relates to a mounting apparatus for use in the suspension systems of vehicles.
Suspension systems making use of elastomeric members or bushings between a generally fixed portion of the frame of the vehicle and an end of a shock absorber, strut, or other type of cylinder or suspension member (hereinafter collectively referred to as a cylinder) are generally well-known within the art. These elastomeric members are generally used to reduce transmitted road noise and suspension vibration, and are also generally flexible enough to allow for articulation or movement of the cylinder during suspension travel. These systems may include such an elastomeric member on each side of the frame to provide dampening during both the compression and extension of the cylinder.
Generally speaking, the greater the loads to which the elastomeric members are subjected, the harder the elastomeric member needs to be to withstand those loads. However, as an elastomeric member gets harder, it tends to provide more resistance to the articulation or movement of the cylinder that takes place during suspension travel. This increased resistance provides a greater torque to the cylinder, which in turn, increases the wear on the cylinder and reduces its useful life.
The suspension systems of heavy-duty vehicles and machinery, such as concrete trucks, dump trucks, and other similar vehicles, must be designed to withstand significantly greater loads and forces than normal passenger cars. One type of suspension system used in many heavy-duty vehicles and machinery consists primarily of a spring, which supports the weight of the vehicle (often referred to as the sprung weight) and a separate shock of some type to limit or dampen the movement of the suspension system. In this type of suspension system, the shock, and therefore the elastomeric members or bushings used to couple the shock to the frame, are not subjected to the weight of the vehicle. Rather, the shock and elastomeric members are subjected only to the damping forces the shock exerts into the system during full jounce and rebound travel of the suspension system.
In another type of suspension system used in heavy-duty vehicles and machinery, the spring and the shock are combined into one unit, which may take the form of a hydraulic and/or pneumatic cylinder. In these systems, the cylinder is subjected to, and must support, the weight of the vehicle as well as the damping forces the cylinder exerts into the system during full jounce and rebound travel of the system. Accordingly, the elastomeric members or bushings used to couple the cylinder to the frame of the vehicle are generally subjected to more force in the jounce direction than they would otherwise be in a system where the spring and shock are separate. In order to withstand these greater forces and loads in the jounce direction, harder elastomeric members or bushings are generally used in the combined spring and shock systems than are used in the separate spring and shock systems. These harder elastomeric members or bushings in the combined spring and shock systems generally provide more resistance to the movement and articulation of the cylinder. Consequently, the cylinder generally wears faster and has a reduced life when compared to a shock in a system where the spring and shock are separate units.
In systems where the shock and the spring are separate, there are generally at least two elastomeric members. One is used to provide dampening during the jounce of the suspension system and the other is used to provide dampening during the rebound of the system. Because of the nature of a conventional shock absorber, which tends to resist movement in either direction, the jounce and rebound elastomeric members are generally subjected to forces that are similar in magnitude. In a suspension system having combined shock and spring units, the jounce elastomeric member is generally subjected to significantly greater forces than is the rebound elastomeric member due to the compounding of the damping forces and the vehicle weight. To account for the different loading conditions, elastomeric members having different properties may be used. However, when elastomeric members having different properties are used, they may expand and contract at different rates, which may cause undesirable gaps to occur between the various elements of the suspension system during its operation.